The term "centre-board" refers to a keel-like structure on a boat that can be raised or lowered to provide stability and steerability. There are several synonyms that can be used to describe this particular part of the boat. One common term is "daggerboard," which is similar in function to a centre-board but is typically found on smaller boats. Other synonyms include "drop keel," "swing keel," and "lifting keel." Each of these terms refers to a mechanism that can be raised or lowered to adjust the boat's depth and stability, allowing for better control and maneuverability in various water conditions. Regardless of the term used, the importance of a good centre-board cannot be overstated when it comes to sailing and boating.